D.C. activist Bryan Weaver said he was surprised to find his name missing from a master list of voters that the D.C. Board of Elections considers to be valid signers of a petition that may lead to a ban on direct corporate contributions to the city’s political campaigns.

He was, after all, the one who spearheaded the effort for the better part of this year. He said another key organizer was missing from the roll as well, but their attorney made the list.

“It’s maddening,” he said.

Their group, the D.C. Committee to Restore Public Trust, plans to argue in D.C. Superior Court on Thursday that the elections board used a confusing and inconsistent system to reject signatures on their petitions for ballot access on Nov. 6, which would allow voters to decide whether to curtail corporate influence in city elections after a scandal-plagued year.

Last month, the board rejected the group’s petitions on the basis of too few signatures, forcing the group to start from scratch and gather more than 23,000 valid signatures in order to qualify for the ballot in a later election.

The group initially accused the board of grossly miscounting its valid signatures. Now, the group says the board failed to mention a color-coded system of green and red checks that determine whether a signature is valid or not, an important detail considering the group pored over black-and-white petition pages while forming its appeal.

“We’re speaking two different languages,” Mr. Weaver said of his group’s deliberations with the board. “We’re looking at the clock running out on us.”

Elections officials argue that members of the group are the ones who failed to follow established rules and did not take steps to accurately monitor the process and research the notation system for eliminating invalid signatures.

In a scathing motion to dismiss, the elections board said the group was simply careless in its “rush” to get the initiative on the general election ballot. The volunteer group counted “OKs” and check marks in the board’s notations without considering additional nuances within the city’s two-phased, color-coded system that determines which signatures are valid and which are not, the board said.

“Had they emphasized accuracy and validity over speed,” the board said, “they might have detected in a timely fashion the numerous address mismatches, duplicate signatures, non-registrant or inactive signers and other defects that have proved fatal for the petition.”

At a status conference Thursday, Judge Laura A. Cordero ordered the petition group to submit a response to the board’s motion to dismiss the case by Tuesday, giving her time to review it Wednesday, before a courtroom showdown the next day. The parties agreed Thursday that the case must be settled by Sept. 9 to allow time to print and distribute absentee ballots 45 days before the election.

The calendar looms large in the trust’s push for the November election, when voters are expected to stream to the polls to cast their ballots for president and a number of D.C. Council seats. Volunteers for the trust had gathered more than 30,000 signatures by fanning out across the city this summer in an effort to stem a stream of scandal and suspicion that has emanated from city hall.

Most notably, federal prosecutors say Mayor Vincent C. Gray’s 2010 campaign benefited from at least $650,000 in undocumented funds, whether the now-mayor knew it or not, from a city contractor hoping to protect his lucrative managed care contract with the District. The development capped off months of uproar over suspicious money orders and bundled contributions that D.C. politicians received from powerful donors who maximized their influence by contributing over and over again through their corporate subsidiaries.

After the trust began its hard-line approach to the issue, Mr. Gray asked the D.C. attorney general to help him develop more nuanced campaign reforms. This week Mr. Gray unveiled the resulting legislation, which among its reforms bans contractors who do big business with the city from donating to political campaigns and forces corporate donors to reveal their stake in subsidiary companies.

Meanwhile, the trust is scrambling to comb over its petition pages and prepare for oral arguments by its attorney, Elizabeth Getman, next week in support of its legal challenge.

To make the ballot, the group had to collect signatures from 5 percent of the city’s voters, including 5 percent of the electorate in each of five of the city’s eight wards to ensure a distribution of input from across the District. The group was given until Sept. 10 to collect the needed signatures. However, in order to get on the November ballot, petition pages had to be submitted by July 9.

But the elections board ruled the petition group had collected 21,572 valid signatures, or 1,726 fewer than the 23,298 needed.

Mr. Weaver on Thursday said the process has been a “massive failure” in terms of open government.

“There clearly seems to be some difference of opinion as to what the methodology was,” Judge Cordero said.